arch/arm/mach-realview/localtimer.c

   1 /*
   2  *  linux/arch/arm/mach-realview/localtimer.c
   3  *
   4  *  Copyright (C) 2002 ARM Ltd.
   5  *  All Rights Reserved
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11 #include <linux/init.h>
  12 #include <linux/kernel.h>
  13 #include <linux/delay.h>
  14 #include <linux/smp.h>
  15 #include <linux/jiffies.h>
  16 #include <linux/clockchips.h>
  17 #include <linux/irq.h>
  18 #include <linux/io.h>
  19
  20 #include <asm/hardware/arm_twd.h>
  21 #include <asm/hardware/gic.h>
  22 #include <mach/hardware.h>
  23 #include <asm/irq.h>
  24
  25 #ifdef CONFIG_LOCAL_TIMERS
  26
  27 /* set up by the platform code */
  28 void __iomem *twd_base;
  29
  30 static unsigned long mpcore_timer_rate;
  31
  32 static void local_timer_set_mode(enum clock_event_mode mode,
  33                                  struct clock_event_device *evt)
  34 {
  35         unsigned long ctrl;
  36
  37         switch(mode) {
  38         case CLOCK_EVT_MODE_PERIODIC:
  39                 /* timer load already set up */
  40                 ctrl = TWD_TIMER_CONTROL_ENABLE | TWD_TIMER_CONTROL_IT_ENABLE
  41                         | TWD_TIMER_CONTROL_PERIODIC;
  42                 break;
  43         case CLOCK_EVT_MODE_ONESHOT:
  44                 /* period set, and timer enabled in 'next_event' hook */
  45                 ctrl = TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT;
  46                 break;
  47         case CLOCK_EVT_MODE_UNUSED:
  48         case CLOCK_EVT_MODE_SHUTDOWN:
  49         default:
  50                 ctrl = 0;
  51         }
  52
  53         __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
  54 }
  55
  56 static int local_timer_set_next_event(unsigned long evt,
  57                                       struct clock_event_device *unused)
  58 {
  59         unsigned long ctrl = __raw_readl(twd_base + TWD_TIMER_CONTROL);
  60
  61         __raw_writel(evt, twd_base + TWD_TIMER_COUNTER);
  62         __raw_writel(ctrl | TWD_TIMER_CONTROL_ENABLE, twd_base + TWD_TIMER_CONTROL);
  63
  64         return 0;
  65 }
  66
  67 /*
  68  * local_timer_ack: checks for a local timer interrupt.
  69  *
  70  * If a local timer interrupt has occurred, acknowledge and return 1.
  71  * Otherwise, return 0.
  72  */
  73 int local_timer_ack(void)
  74 {
  75         if (__raw_readl(twd_base + TWD_TIMER_INTSTAT)) {
  76                 __raw_writel(1, twd_base + TWD_TIMER_INTSTAT);
  77                 return 1;
  78         }
  79
  80         return 0;
  81 }
  82
  83 static void __cpuinit twd_calibrate_rate(void)
  84 {
  85         unsigned long load, count;
  86         u64 waitjiffies;
  87
  88         /*
  89          * If this is the first time round, we need to work out how fast
  90          * the timer ticks
  91          */
  92         if (mpcore_timer_rate == 0) {
  93                 printk("Calibrating local timer... ");
  94
  95                 /* Wait for a tick to start */
  96                 waitjiffies = get_jiffies_64() + 1;
  97
  98                 while (get_jiffies_64() < waitjiffies)
  99                         udelay(10);
 100
 101                 /* OK, now the tick has started, let's get the timer going */
 102                 waitjiffies += 5;
 103
 104                                  /* enable, no interrupt or reload */
 105                 __raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);
 106
 107                                  /* maximum value */
 108                 __raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
 109
 110                 while (get_jiffies_64() < waitjiffies)
 111                         udelay(10);
 112
 113                 count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
 114
 115                 mpcore_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
 116
 117                 printk("%lu.%02luMHz.\n", mpcore_timer_rate / 1000000,
 118                         (mpcore_timer_rate / 100000) % 100);
 119         }
 120
 121         load = mpcore_timer_rate / HZ;
 122
 123         __raw_writel(load, twd_base + TWD_TIMER_LOAD);
 124 }
 125
 126 /*
 127  * Setup the local clock events for a CPU.
 128  */
 129 void __cpuinit local_timer_setup(struct clock_event_device *evt)
 130 {
 131         unsigned long flags;
 132
 133         twd_calibrate_rate();
 134
 135         evt->name               = "local_timer";
 136         evt->features           = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
 137         evt->rating             = 350;
 138         evt->set_mode           = local_timer_set_mode;
 139         evt->set_next_event     = local_timer_set_next_event;
 140         evt->irq                = IRQ_LOCALTIMER;
 141         evt->shift              = 20;
 142         evt->mult               = div_sc(mpcore_timer_rate, NSEC_PER_SEC, evt->shift);
 143         evt->max_delta_ns       = clockevent_delta2ns(0xffffffff, evt);
 144         evt->min_delta_ns       = clockevent_delta2ns(0xf, evt);
 145
 146         /* Make sure our local interrupt controller has this enabled */
 147         local_irq_save(flags);
 148         get_irq_chip(IRQ_LOCALTIMER)->unmask(IRQ_LOCALTIMER);
 149         local_irq_restore(flags);
 150
 151         clockevents_register_device(evt);
 152 }
 153
 154 /*
 155  * take a local timer down
 156  */
 157 void __cpuexit local_timer_stop(void)
 158 {
 159         __raw_writel(0, twd_base + TWD_TIMER_CONTROL);
 160 }
 161
 162 #endif  /* CONFIG_LOCAL_TIMERS */